1. Field of the Invention.
The present invention relates to pumping apparatus. In particular, the present invention relates to a rolling diaphragm type pump.
2. Description of the Prior Art.
To improve health care, there has been considerable effort with regard to the administration of intravenous (IV ) fluid. For many years IV solutions were administered only by the force of gravity. The volume rate was measured by counting the number of drops per minute. In many instances this method proved unsatisfactory. Drop size is directly proportional to surface tension, which is affected by viscosity, temperature, type of solution, and also drop size is affected by the speed at which the drop forms. The drop rate is affected by the gravitation force and the restrictions of the tube and needle. If a tube is partly occluded, the drop rate will decrease or as the IV supply decreases the hydrostatic pressure will decrease causing a decrease in drop rate. In many cases, therefore, the variability of both the drop size and the drop rate (both of which are for the most part beyond the control of the operator) makes this method of administration of intravenous fluid unsatisfactory.
Improvements have been made by adding an electronic drop counter together with either a controller or a peristaltic pump. The electronic drop counter and controller combination controls the drop rate but makes no improvements in controlling drop size, and also has the deficiency of not being able to control drop rate if back pressure increases beyond the hydrostatic forcing pressure. The electronic drop counter and peristaltic pump combination increase the forcing pressure but lacks an accurate metering method.
Improvement in metering methods results with the use of displacement pumps, which offer the capability of greater precision in controlling IV flow rates than is possible with the prior art IV controllers which depend on gravity. These pumps, in addition to metering the fluid, also apply positive pressure to the fluid or the IV tubing.